Abstract
<p>Purpose: Simultaneous alcohol and cannabis use is a common type of polysubstance use amongyoung adults. Depending on the substance used first, the amount of alcohol consumed might vary.Coping or enhancement motives endorsed on simultaneous use days might also impact alcoholconsumption differently. This study examined whether alcohol use differed on alcohol-only versussimultaneous use days, and whether using alcohol versus cannabis first on a simultaneous use daypredicted heavier alcohol consumption. We also examined whether differences in alcoholconsumption depended on daily levels of coping or enhancement motives.Methods: Undergraduate students (n = 370; Mage=20.8; SD = 1.5) completed a 14-weekend daily diarystudy in Fall 2021. Surveys administered Friday to Sunday mornings measured alcohol use, cannabisuse, their order of use, number of drinks consumed, and motives for simultaneous use. Analyseswere restricted to alcohol-only and simultaneous use days (n = 2826/9017; 31.3%).Results: Multilevel models showed that students consumed more alcohol on simultaneous use days(Mdrinks=5.08) than alcohol-only days (Mdrinks=4.23). Students also consumed about 1.4 fewer drinkswhen cannabis was used first compared to when alcohol was used first on simultaneous use days.However, the effect of order of use on alcohol consumption did not depend on daily levels ofcoping or enhancement motives.Conclusions: Using cannabis first on simultaneous use days was associated with less drinking, aneffect not apparently linked to situational drinking motives. Contextual factors associated withcannabis use such as affect (e.g., negative or positive) and setting (e.g., alone or with others) mayexplain lighter drinking on cannabis-first simultaneous use days.</p>